diff --git a/packages/frontend/src/custom-emojis.ts b/packages/frontend/src/custom-emojis.ts
index 0d03282ce..4009ed703 100644
--- a/packages/frontend/src/custom-emojis.ts
+++ b/packages/frontend/src/custom-emojis.ts
@@ -8,69 +8,128 @@ import * as Misskey from 'misskey-js';
 import { misskeyApi, misskeyApiGet } from '@/scripts/misskey-api.js';
 import { get, set } from '@/scripts/idb-proxy.js';
 
+const CACHE_EXPIRE_TIME = 60 * 60 * 1000;
+const BATCH_SIZE = 1000;
+
 const storageCache = await get('emojis');
-export const customEmojis = shallowRef<Misskey.entities.EmojiSimple[]>(Array.isArray(storageCache) ? storageCache : []);
-export const customEmojiCategories = computed<[ ...string[], null ]>(() => {
-	const categories = new Set<string>();
-	for (const emoji of customEmojis.value) {
-		if (emoji.category && emoji.category !== 'null') {
-			categories.add(emoji.category);
+export const customEmojis = shallowRef<Misskey.entities.EmojiSimple[]>(
+	Array.isArray(storageCache) ? storageCache : [],
+);
+
+const categoriesMap = new Map<string, Misskey.entities.EmojiSimple[]>();
+
+export const customEmojiCategories = computed<[...string[], null]>(() => {
+	if (categoriesMap.size === 0 && customEmojis.value.length > 0) {
+		for (const emoji of customEmojis.value) {
+			const category = emoji.category && emoji.category !== 'null'
+				? emoji.category
+				: 'null';
+
+			if (!categoriesMap.has(category)) {
+				categoriesMap.set(category, []);
+			}
+			categoriesMap.get(category)?.push(emoji);
 		}
 	}
-	return markRaw([...Array.from(categories), null]);
+	return markRaw([...Array.from(categoriesMap.keys()), null]);
 });
 
 export const customEmojisMap = new Map<string, Misskey.entities.EmojiSimple>();
-watch(customEmojis, emojis => {
+
+function batchUpdateMap(emojis: Misskey.entities.EmojiSimple[]): void {
 	customEmojisMap.clear();
-	for (const emoji of emojis) {
-		customEmojisMap.set(emoji.name, emoji);
-	}
-}, { immediate: true });
+	categoriesMap.clear();
 
-export function addCustomEmoji(emoji: Misskey.entities.EmojiSimple) {
-	customEmojis.value = [emoji, ...customEmojis.value];
-	set('emojis', customEmojis.value);
-}
-
-export function updateCustomEmojis(emojis: Misskey.entities.EmojiSimple[]) {
-	customEmojis.value = customEmojis.value.map(item => emojis.find(search => search.name === item.name) ?? item);
-	set('emojis', customEmojis.value);
-}
-
-export function removeCustomEmojis(emojis: Misskey.entities.EmojiSimple[]) {
-	customEmojis.value = customEmojis.value.filter(item => !emojis.some(search => search.name === item.name));
-	set('emojis', customEmojis.value);
-}
-
-export async function fetchCustomEmojis(force = false) {
-	const now = Date.now();
-
-	let res;
-	if (force) {
-		res = await misskeyApi('emojis', {});
-	} else {
-		const lastFetchedAt = await get('lastEmojisFetchedAt');
-		if (lastFetchedAt && (now - lastFetchedAt) < 1000 * 60 * 60) return;
-		res = await misskeyApiGet('emojis', {});
-	}
-
-	customEmojis.value = res.emojis;
-	set('emojis', res.emojis);
-	set('lastEmojisFetchedAt', now);
-}
-
-let cachedTags;
-export function getCustomEmojiTags() {
-	if (cachedTags) return cachedTags;
-
-	const tags = new Set();
-	for (const emoji of customEmojis.value) {
-		for (const tag of emoji.aliases) {
-			tags.add(tag);
+	for (let i = 0; i < emojis.length; i += BATCH_SIZE) {
+		const batch = emojis.slice(i, i + BATCH_SIZE);
+		for (const emoji of batch) {
+			customEmojisMap.set(emoji.name, emoji);
 		}
 	}
-	const res = Array.from(tags);
-	cachedTags = res;
-	return res;
+}
+
+watch(customEmojis, emojis => {
+	batchUpdateMap(emojis);
+}, { immediate: true });
+
+export function addCustomEmoji(emoji: Misskey.entities.EmojiSimple): void {
+	const newEmojis = [emoji, ...customEmojis.value];
+	customEmojis.value = newEmojis;
+	customEmojisMap.set(emoji.name, emoji);
+	void set('emojis', newEmojis);
+}
+
+export function updateCustomEmojis(emojis: Misskey.entities.EmojiSimple[]): void {
+	const updateMap = new Map(emojis.map(emoji => [emoji.name, emoji]));
+
+	const newEmojis = customEmojis.value.map(item =>
+		updateMap.get(item.name) ?? item,
+	);
+
+	customEmojis.value = newEmojis;
+	batchUpdateMap(newEmojis);
+	void set('emojis', newEmojis);
+}
+
+export function removeCustomEmojis(emojis: Misskey.entities.EmojiSimple[]): void {
+	const removedNames = new Set(emojis.map(e => e.name));
+
+	const filteredEmojis = customEmojis.value.filter(
+		item => !removedNames.has(item.name),
+	);
+
+	customEmojis.value = filteredEmojis;
+	batchUpdateMap(filteredEmojis);
+	void set('emojis', filteredEmojis);
+}
+
+export async function fetchCustomEmojis(force = false): Promise<void> {
+	const now = Date.now();
+
+	if (!force) {
+		const lastFetchedAt = await get('lastEmojisFetchedAt');
+		if (lastFetchedAt && (now - lastFetchedAt) < CACHE_EXPIRE_TIME) {
+			return;
+		}
+	}
+
+	try {
+		const res = await (force ? misskeyApi : misskeyApiGet)('emojis', {});
+
+		if (res.emojis.length > 0) {
+			customEmojis.value = res.emojis;
+			await Promise.all([
+				set('emojis', res.emojis),
+				set('lastEmojisFetchedAt', now),
+			]);
+		}
+	} catch (error) {
+		console.error('Failed to fetch emojis:', error);
+	}
+}
+
+const tagsCache = new Map<string, string[]>();
+
+export function getCustomEmojiTags(): string[] {
+	const cacheKey = `${customEmojis.value.length}`;
+
+	if (tagsCache.has(cacheKey)) {
+		const cached = tagsCache.get(cacheKey);
+		if (cached) return cached;
+	}
+
+	const tags = new Set<string>();
+
+	for (let i = 0; i < customEmojis.value.length; i += BATCH_SIZE) {
+		const batch = customEmojis.value.slice(i, i + BATCH_SIZE);
+		for (const emoji of batch) {
+			for (const tag of emoji.aliases) {
+				tags.add(tag);
+			}
+		}
+	}
+
+	const result = Array.from(tags);
+	tagsCache.set(cacheKey, result);
+	return result;
 }